Hammers with replaceable striking face



Feb. 6, 1962 w. E. P. JEFFERY ETAL 3,019,827

HAMMERS WITH REPLACEABLE STRIKING FACE Filed Dec. 28, 1959 h J Edgy Inventors WENSTONE ERIC PAYTON JEFFERY WALTER RUNC IMAN STEPHENS United States Patent Office asiaszr Patented Feb. 6, 1 962 3,019,827 HAMMERS WITH REPLACEABLE STRIKING FACE This invention relates to hammers, and whilst it is primarily concerned with hand hammers having a shaft and a head, it is also applicable to other percussive tools such as, for example, tampers and the like which may not be equipped with a shaft. The expression hammer is therefore used herein in a generic sense to include all kinds of percussive tools.

The invention is concerned with hammers which have a renewable striking face or faces being made from a relatively soft synthetic resinous material, which is relatively soft when compared with a very hard material such as steel.

One of the objects of the present invention is to provide improvements in such hammers whereby the possibility of a renewable face becoming loosened during working will be eliminated or substantially reduced.

According to the present invention we provide a hammer of the kind hereinbefore referred to, comprising a head portion of a relatively hard material (eg a metal such as steel) and one or more renewable face portions of a relatively soft synthetic resinous material each face portion having a screw threaded part adapted to be engaged with a corresponding screw threaded part of the head portion, and the face portion and head portion having co-operating mutually engaging surfaces which are remote from the screw threaded parts and which are wholly or in part of dissimilar or non-mating configuration such that, when the face and head portions are engaged together, application of pressure tending to force the two together causes the soft material of the face portion to be distorted over the region or regions of the said mutually engaging surfaces into mating engagement with the hard material of the head portion, so as to form between the two, a locking engagement which resists rotation of the face portion relative to the head portion.

. The locking engagement between the face portion and head portion is preferably such as to provide enough resistance to prevent loosening of the face portion under normal conditions, but still permit of the face portion portion, which portion may be formed of steel, with a v renewable face portion disposed at each end of the head portion and in a preferred embodiment of this form of hammer each face portion has an externally threaded stem which is engageable in an internally threaded hole in each end of the head portion.

A further aspect of the present invention has relation to improving the strength and durability of the form of hammer in which the renewable face portion comprises a striking part and an externally screw threaded stem extending away from the striking part. In this form the diameter of the stem is appreciably less than the dimensions of the striking part measured in the radial direction.

According to this aspect of the invention the radial dimension of the striking part is reduced progressively, or in one or more stages, at the junction between the striking part and the screwed stem, this reduction being from the maximum dimension down to the diameter of the screwed stem.

In this way there is avoided the presence of any sharp angular corner between the screwed stem and the striking part of the face portion.

The above feature may be achieved by having a smooth corner fillet between the striking part and the screwed stem, or in the more common form of a face portion 1n which the striking part is of circular cross-section, the above arrangement may be achieved by the provision of an intermediate shoulder in between the striking part and the screwed stem;

There are various ways of forming the co-operating mutually engaging surfaces on each face portion and the head portion. Certain embodiments of the invention are described hereinafter, by way of example, and are illustrated in the accompanying drawings, wherein:

FIGURE 1 is a View showing a hammer head with two striking faces, one being shown removed;

FIGURE 2 is a fragmentary View of a hammer head showing an alternative form;

FIGURES 3 and 4 are fragmentary sections showing alternative forms of hammer heads and striking faces.

Referring to the accompanying drawings FIGURE 1 illustrates the head of a hammer and it Will be seen that it comprises a head portion 11 made of a suitable steel and provided with an opening 12 extending thereth rough in which is fixed the end of the shaft or handle and at each end the head portion 11 is provided with a renewable face portion iii. Each face portion 1i comprising a striking part 13 and an axially projecting externally threaded stem 14 which can have screwed engagement with an axially extending internally threaded opening 15 in the adjacent end of the head portion 11.

It will also be seen that the threaded stem 14 projects axially from a portion of the striking part 13 which is of reduced diameter and which provides a shoulder 16,

. this shoulder 16 being seen more clearly in the modification shown in FIGURE 3 and its function and purpose being referred to more particularly hereafter.

The end of the head portion 11 is provided with a circular recess 17 surrounding the threaded opening 15' and dimensioned to receive the shoulder 16 on the face portion 10.

The base of this recess and the rim of the Wall surrounding the recess are provided with the surface locking formations which, in this case, are in the form of radially extending shallow grooves 18 and 19 respectively, and these co-operate with the opposed plain surfaces on the underside of the face portion 10.

FIGURE 2 illustrates a similar form of head portion 11 with which would be used a face portion 10 of the same construction as shown in FIGURE 1 and in the case of FIGURE 2 the surface locking formations take the form ofratchet teeth-20 and 21 respectively, formed in the base of the recess 17 and upon the rim of the annular wall surrounding this recess.

Alternatively, or in addition to the locking formations described in FIGURES l and 2 the internal wall of the recess 17 may be formed with locking formations such as axially extending serrations or teeth and these would co-operate with the plain surface of the shoulder 16.

In the further alternative embodiment illustrated in FIGURE 3 the striking part 13 of the face portion 10 is formed as in FIGURE 1 with the axially projecting screwed stem 14 which projects from the reduced diameter part providing a shoulder 16 and, in this case, the striking part 13 is provided at its periphery with an axially extending flange 22 which, when the face portion 10 is screwed into engagement with the headportion 11, telescopes over the outer end of the head portion 11. In this case the locking formations may be provided around a a the periphery of the outer end of the head portion 11 and may be in the form of grooves, serrations or teeth as indicated at 23. If desired, in addition to the formations at 23 additional formations may be provided in the places indicated in FIGURES 1 and 2.

In a further modification, not illustrated in the drawings, the head portion 11 may be provided with a further screwthreaded part of opposite hand or of different pitch to the screw thread 15 which engages the threaded stem 14 on the face portion and this other screw threaded part of the head portion would be engaged by a plain part on the face portion. For example, this extra screw threaded part may be provided around the periphery of the head portion at the position 23 as indicated in the construction shown in FIGURE 3.

It will be appreciated from the above examples that when the face portion 10 is screwed into engagement with the head portion 11, the plain surface or surfaces on the face portion are brought into engagement with the particular surface locking formations on the head portion and become distorted so as to make locking engagement with these formations on the head portion. After assembly a final application of pressure may be applied, such as in a press, to complete the process of distortion and force the co-operating surfaces into tight engagement, or instead of this, the first few blows of the hammer when being used can be relied upon to provide this pressure for bedding down the co-operating surfaces.

Instead of having a co-operating surface or surfaces which is or which are plain, the face portion may also have surface formations providing these are such as to be of a non-mating character when compared with the particular formation on the head portion, otherwise the interference between the two portions would not be provided.

The reduced diameter portion which provides the shoulder 16 indicated in FIGURES 1 and 3 may take other forms such as that illustrated in FIGURE 4 wherein the screwed stem 14 extends axially from a part-spherical or domed boss 24 which is of reduced diameter as compared with the diameter of the striking part 13 and the head portion 11 of the hammer would be provided with a recess 25 of corresponding part-spherical formation.

In this case the surface locking formations may be provided around the periphery of this recess 25 as indicated at 26 and may be grooves, serrations, ratchet teeth or the like. Alternatively, or in addition, such locking formations may be provided in the base of the recess 25.

The provision of this shoulder gives added strength to the face portion as a whole and removes the danger of any high concentration of stres which might occur in the sharp corner between the striking part and the screwed stem as it is at this position that breakage is likely to occur.

The shoulder has a further advantageous feature in providing resistance to forces in the direction radially or laterally to the axis of the screwed stem. When in use the forces encountered by the face portion are not truly axially applied forces because in practice, fewif any blows are delivered exactly along the axis of the stem and in the main the blows occur at an angle to the axis of the stem, so that there is an appreciable radial component of force acting upon the stem and the presence of the shoulder materially strengthens the resistance of the face portion to these radial forces; 7

The features of the present invention lend themselves admirably to the production of the face portion from various plastic materials amongst which nylon has been found to provide advantageous characteristics.

What we claim then is:

1. A hammer comprising a head portion of hard metal and a renewable face portion of a relatively soft synthetic resinous material having a screw threaded stern for engagement with an internally threaded hole provided in the head portion, the face portion having a plain surface surrounding said stern and the end of the head around said internally threaded hole being provided with a locking surface which is engaged by said plain surface on the face portion, said locking surface having a series of angularly spaced indentations around said internally threaded opening, wherein the head portion has a series of angularly spaced radially extending grooves provided on a fiat surface which is on the end face of the head portion in a plane at right angles to the axis of the said internally threaded hole.

2. A hammer comprising a head portion of hard metal and a renewable face portion of a relatively soft synthetic resinous material having a screw threaded stern for engagement with an internally threaded hole provided in the head portion, the face portion having a plain surface surrounding said stern and the end of the head around said internally threaded hole being provided with a locking surface which is engaged by said plain surface on the face portion, said locking surface having a series of angularly spaced indentations around said internally threaded opening, wherein the head portion has an annular recess in its end face surrounding said internally threaded hole, the base of the recess being in a plane at right angles to the axis of said hole and forming said locking surface, said indentations being constructed in the form of radially extending grooves and the wall surrounding said recess being provided on its annular end face with a series of angularly spaced radially extending grooves which are staggered in relation to the grooves in the base of the annular recess.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Nupla Catalog, 5,451, May 5, 1955. 

